Only 20 percent of teens get the recommended nine hours of shuteye on school nights, and more than one in four report sleeping in class, according to a poll by the National Sleep Foundation released Tuesday.
What's more, the poll finds that parents are mostly in the dark about their adolescents' sleep habits. While most students know they're not getting the sleep they need, 90 percent of parents polled believe their adolescents are getting enough sleep on school nights.
A quick sampling of teens by CBS News Correspondent Thalia Assuras found the poll was on target, with most saying they have trouble getting up in the morning.
Carl Woock, a 17-year-old high school senior from Bethesda, Md.,
"In the competition between the natural tendency to stay up late and early school start times, a teen's sleep is what loses out," said Jodi A. Mindell of St. Joseph's University in Philadelphia.
"Sleep serves not only a restorative function for adolescents' bodies and brains, but it is also a key time when they process what they've learned during the day," said Mindell, who is also associate director of the Sleep Center at The Children's Hospital of Philadelphia.
But Owens said puberty changes the body's "circadian rhythm."
"An 8- or 9- or 10-year-old is able to fall asleep at 9 at night," she told Assuras, "but a 13-, 14-, 15-year-old has their circadian rhythm shifted, so that they're not able to fall asleep until 10, 11, or 12 at night naturally."
The Sleep Foundation's poll found that sixth-graders were sleeping an average of 8.4 hours on school nights, while 12th- graders sleep just 6.9 hours, two hours less than recommended.
Without enough sleep, a person has trouble focusing and responding quickly, according to the NIH. The agency also said there is growing evidence linking a chronic lack of sleep with an increased risk of obesity, diabetes, heart disease and infections.
Brown Medical School Professor of Pediatrics Dr. Judith Owens warned Assuras there's more in a teen's life that's affected by sleep deprivation.
"They are moody," Owens said. "Depression is a concern. It affects every aspect of their lives."
The Sleep Foundation poll interviewed 1,602 adult caregivers and their children aged 11 to 17. It had a margin of error of 2.4 percentage points.
Among the findings:
One teen told Assuras, "As soon as I get home, I'm online until I go to sleep."
Assuras notes that, for many teens, one solution to the sleep dynamic comes in a cup, with many saying they drink lots of coffee, espresso, and more.
The caffeine may help teens perk up during the day, Assuras points out, but it only masks the underlying biological reason for their sleep habits — the natural inclination to go to bed late caused by those natural body rhythm changes.
Some school districts, most notably the Minneapolis public school district, have been trying later start times for high schools, Assuras reports. Researchers have seen some benefits, but in many school districts, conflicts with bus schedules and after-school activities make such changes extremely difficult.
Assuras says, short of getting school start times changed, teens might want to take some advice from experts, who recommend saying goodbye to the entertainment zone in the bedroom, cutting out caffeine after lunchtime, setting up a daily sleep and wake-time routine, and being aware that trying to catch up by sleeping in on weekends throws off your natural body rhythm.